1. Field of the Invention
The present invention generally relates to a magnetic recording medium and more particularly is directed to a magnetic recording medium in which a magnetic metal thin film is deposited on a non-magnetic substrate.
2. Description of the Prior Art
A conventional magnetic recording medium which is provided in such a manner that a magnetic paint composed of acicular magnetic powder and polymeric binder is coated on a non-magnetic substrate to form a magnetic recording layer thereon is generally used.
On the other hand, a magnetic metal thin film magnetic recording medium which is formed by such a manner that magnetic metal such as Co, Fe, Ni and so on or alloy of them is deposited on a non-magnetic substrate according to a so-called physical vapor deposition technique such as vacuum evaporation, sputtering or ion plating and so on is now noted. Since the magnetic recording medium of the magnetic metal thin film type needs no non-magnetic binder, it can present significantly high residual magnetic flux density. In addition, since the magnetic material layer thereof can be formed quite thin, this magnetic recording medium produces a high output and is superior in short wavelength response characteristic.
However, with mere vapor evaporation of magnetic metal such as Co or the like on the non-magnetic substrate, it is difficult to obtain a magnetic layer having high coercive force. Therefore, as a method for forming a magnetic recording layer which has high coercive force, a so-called oblique evaporation method is proposed in which vapor of magnetic metal particles is obliquely incident on a non-magnetic substrate thereby deposited. This oblique evaporation method, however, has poor vapor evaporation efficiency and productivity is low.